The present invention relates to a semiconductor device having a package structure such as BGA (Ball Grid Array), CSP (Chip Scale Package), wherein a semiconductor chip is mounted on a circuit board through a resin layer, and a method of manufacturing the same.
Semiconductor devices have been increasingly required to be lighter and smaller, in accordance with the recent trend that electronic devices have become lighter and smaller. Corresponding with this trend, BGA or CSP-type semiconductor devices using a sealing resin have become widely used.
FIG. 8(a) shows an example of a conventional wire bonding type CSP. This semiconductor device is arranged so that a semiconductor chip 51 is fixed on a circuit board 52 by using an adhesive film or an adhesive resin paste layer 53. The semiconductor chip 51 is connected to a metal wire 54 formed on the top surface of the circuit board 52 by a wire 55 (wire bonding) and the metal wire 54 is connected to a solder ball 56 formed on the bottom surface of the circuit board 52, through a perforation 57 formed through the circuit board 52. This semiconductor device is arranged so that a face of the circuit board 52 where the semiconductor chip is mounted is coated with a resin mold layer 58 to protect the semiconductor chip 51 and the wire 55.
FIG. 8(b) shows an example of a conventional flip chip type CSP. This semiconductor device is arranged so that the semiconductor chip 51 is fixed on the top surface of the circuit board 52 by using the adhesive resin layer 53. The adhesive resin layer 53 is fabricated from an insulating or anisotropic conductive paste or sheet. Each protrusive electrode 59 formed on an electrode (not illustrated) of the semiconductor chip 51 is connected to an electrode of the circuit board 52, and the metal wire 54 on the circuit board 52 is also connected to the solder ball 56 provided on the bottom surface of the circuit board 52 through the perforation 57 formed on the circuit board 52.
As another method to mount the semiconductor chip 51 on the circuit board 52 by a flip chip connection, there is a method in which a liquid sealing resin is injected into an interface between the semiconductor chip 51 and the circuit board 52, after the semiconductor chip 51 is connected to the circuit board 52 by the flip chip connection. In the cases of these flip chip connections, the resin mold layer 58 is not necessary.
When the semiconductor devices shown in FIGS. 8(a) and (b) are used, the device is mounted on another packaging substrate by reflowing. However, the constituents of the semiconductor device such as a base material forming the circuit board 52 and a resin take up moisture in the air. The moisture is vaporized and expands as the temperature rises at the moment of mounting by reflowing, so this may bring about the so-called popcorn phenomenon that causes swelling and falling off inside the semiconductor device. In this manner, the moisture in the semiconductor device has been a problem.
Thus, as FIG. 9(a) shows, a technique (first conventional technique) of Japanese Laid-Open Patent Application No. 9-121002/1997 (Tokukaihei 9-121002; published on May 6, 1997) is arranged so that a small hole, i.e. moisture drain hole 60 penetrating the circuit board 52 is formed in an area of the circuit board 52 where the adhesive resin layer 53 is exposed, and the moisture accumulated in the semiconductor device is effectively drained through the moisture drain hole 60.
Meanwhile, as FIG. 9(b) shows, a technique (second conventional technique) of Japanese Laid-Open Patent Application No. 11-243160/1999 (Tokukaihei 11-243160; published on Sep. 7, 1999) proposes such an arrangement that a small hole, i.e. moisture drain hole 61, penetrating the circuit board 52 and the adhesive resin layer 53 from the bottom surface of the circuit board 52, is formed to make it easy to drain the moisture through th e moisture drain hole 61.
However, the conventional semiconductor devices have following problems. The first conventional technique is arranged so that the moisture drain hole 60 is formed before the semiconductor chip 51 is mounted on the circuit board 52. In this kind of arrangement, fluid adhesives such as an adhesive like a paste or resins that temporarily lose solidity so as to becoming fluid when heated cannot be used as materials for the adhesive resin layer 53 for mounting the semiconductor substrate 51 on the circuit board 52. This is because the adhesive or the resin could leak through the moisture drain hole 60 or the hole 60 could be blocked by the leaking agent. For the same reasons, in the case of the flip chip connection, an aerotropic conductive adhesive film/paste, a thermosetting adhesive, or an underfill agent cannot be used as the adhesive resin layer 53. As a result, available materials and variety of the manufacturing process have become severely limited.
In the meantime, the second conventional technique is arranged so that the moisture drain hole 61 is formed through the circuit board 52 and the adhesive resin layer 53 after the semiconductor chip 51 is mounted on the circuit board 52, to solve these problems.
However, in this case it is difficult to determine the endpoint in the penetrating operation, when the moisture drain hole 61 is formed from the bottom surface of the circuit board 52 by using a drill or a laser beam. That is to say, provided that the semiconductor device is the wire bonding type shown in FIG. 9(b), on the one hand, it is possible to set the endpoint as the penetrating operation ends when the laser beam reaches the back of the semiconductor chip 51, since a non-connecting surface of the semiconductor chip 51 faces the circuit board 52. On the other hand, in the case of a flip-chip-type semiconductor device, since the laser beam reaches a connecting surface (top surface) of the semiconductor chip 51, the laser beam does harm to characteristics of the semiconductor device, because a connecting surface of the semiconductor chip 51 faces the circuit board 52. Moreover, moisture resistance of the semiconductor chip 51 has become reduced, because the connecting surface of the semiconductor chip 51 is exposed to the outside air through the moisture drain hole 61.
In both of the conventional techniques, performance of draining moisture from the semiconductor device depends on the diameter of the moisture drain holes 60 and 61, so the larger the diameter, the better moisture draining performance. Meanwhile, the diameter of the moisture drain holes 60 and 61 are determined in accordance with the diameter of the laser beam or the drill forming the holes 60 and 61. For instance, when the laser beam which can do the operation efficiently is used, it is difficult to make a beam with large diameter and thus making the moisture drain holes 60 and 61 have large diameter is also difficult. In the meantime, when the drill is used, while making the moisture drain holes 60 and 61 with large diameter itself is easy, it is difficult to drain moisture adequately by making the diameter of the moisture drain holes 60 and 61 be adequately large, because relationships such as tradeoffs between the moisture drain hole and the wiring pattern (metal wire 54) formed on the circuit board 52 must be considered.
Therefore, the present invention aims to provide a semiconductor device capable of efficiently draining moisture from the device through a moisture drain hole formed through a circuit board, at the moment of reflowing for mounting the semiconductor device on another mounting substrate. Furthermore, the present invention aims to provide a manufacturing method of a semiconductor device in which:
a semiconductor chip is protected from a penetrating operation to form the moisture drain hole through the circuit board; and also
materials of intermediate layers such as an adhesive resin layer, situated between the circuit board and a semiconductor chip, can be prevented from leaking through the moisture drain hole of the circuit board, when the semiconductor chip is mounted on the circuit board.
To solve the problems above, a semiconductor device of the present invention includes:
a circuit board provided with a moisture drain hole formed therethrough and a semiconductor chip mounted thereon via an intermediate layer (for instance an adhesive resin layer for fixing the semiconductor chip on the circuit board or a resin layer such as a solder resist layer), wherein a pit part having a width greater than a diameter of the moisture drain hole is formed in a part of the intermediate layer facing the moisture drain hole.
According to this arrangement, for instance, moisture contained in:
a mold resin layer for sealing the semiconductor chip;
the adhesive resin layer or the solder resist layer, the intermediate layer between the circuit board and the semiconductor chip, fixing the semiconductor chip on the circuit board; and
the circuit board on which the semiconductor chip is mounted, is drained as, for instance, steam, through the pit part formed in the intermediate layer and the moisture drain hole formed through the circuit board, when, for instance, the semiconductor device is mounted on another packaging substrate by reflowing.
In this case, since the width of the pit part formed in the intermediate layer is wider than the diameter of the moisture drain hole formed through the circuit board, draining moisture can be done efficiently without enlarging the diameter of the moisture drain hole, compared to the case when the width of the pit part is as wide as the diameter of the moisture drain hole. This makes it possible to properly prevent, for instance, the intermediate layer or the mold resin from peeling off from the circuit board, which is caused by the expansion of the steam generated in the process of reflowing inside the semiconductor device.
A manufacturing method of the semiconductor device of the present invention, arranged so that a semiconductor chip is mounted on a face of the circuit board via an intermediate layer (for instance, an adhesive resin layer for fixing the semiconductor chip on the circuit board and a resin layer such as a solder resist layer) a moisture drain hole is formed through the circuit board, includes the steps of:
(a) forming a tentative protective wire for covering a mouth of the moisture drain hole opened on the face on an area of the face where the moisture drain hole is formed;
(b) after step (a), mounting the semiconductor chip on the face via the intermediate layer;
(c) after step (a), forming the moisture drain hole through the circuit board from a face, of the circuit board, opposite to the face; and
(d) after step (b), removing the tentative protective wire through the moisture drain hole.
According to this arrangement, in step (a), a tentative protective wire, covering a mouth of the moisture drain hole opened on the face, is formed on an area of the face where the moisture drain hole is formed, then in step (b) after step (a), the semiconductor chip is mounted on the face via the intermediate layer. Then in step (c) after step (a) , the moisture drain hole is formed through the circuit board from a face, of the circuit board, opposite to the face. The moisture drain hole is formed using a laser beam, and the formation thereof ends when the laser beam penetrates the circuit board and reaches the tentative protective wire. Then in step (d) after step (b), the tentative protective wire is removed through the moisture drain hole. This is done through the moisture drain hole by, for instance, etching. The pit part, linked with the moisture drain holes and shaped like the tentative protective wire, is formed as a result of these steps.
Consequently, it is possible in step (b) to prevent materials contained in the intermediate layer, for instance, the adhesive resin for fixing the semiconductor chip on the circuit board and resin materials such as the solder resist, from flowing out through the moisture drain hole.
Moreover, when the laser beam is used to form the moisture drain hole in the circuit board in step (c), it is easy to determine the endpoint in the penetrating operation by the laser beam, since the operation is supposed to end when the laser beam penetrates the circuit board and reaches the tentative protective wire. This prevents the semiconductor chip from being damaged and features thereof from being deteriorated due to projection of the laser beam thereon. Moreover, it is possible to prevent degradation of moisture resistance of the semiconductor chip due to the exposure to the outside-air.
Furthermore, the tentative protective wire is formed for covering a mouth of the moisture drain hole opened on the face for mounting the semiconductor chip so that the pit part formed by removing the tentative protective wire should have a width wider than the diameter of the moisture drain hole. Thus this makes it possible to drain moisture through the pit part and the moisture drain hole of the semiconductor device efficiently without enlarging the diameter of the moisture drain hole, compared to the case when the width of the pit part is as wide as the diameter of the moisture drain hole. Then this makes it possible to properly prevent, for instance, the intermediate layer or the mold resin from peeling off from the circuit board, which is caused by the expansion of the steam generated in the process of reflowing inside the semiconductor device.
A manufacturing method of a semiconductor device in accordance with the present invention including a circuit board provided with a moisture drain hole formed therethrough and a semiconductor chip mounted on a face thereof via an intermediate layer (for instance, an adhesive resin layer for fixing the semiconductor chip on the circuit board and a resin layer such as a solder resist layer), includes the steps of:
(a) forming the moisture drain hole on the face;
(b) after step (a), forming on the face a tentative protective wire for covering a mouth of the moisture drain hole opened on the face;
(c) after step (b), mounting the semiconductor chip on the face via the intermediate layer; and
(d) after step (c), removing the tentative protective wire through the moisture drain hole.
According to this arrangement, it is possible in step (c) to prevent materials, for instance, the adhesive resin for fixing the semiconductor chip on the circuit board and resin materials such as the solder resist, contained in the intermediate layer from flowing out through the moisture drain hole, since the tentative protective wire covers a mouth of the moisture drain hole opened on the face.
Moreover, carrying out step (a) before step (c) prevents the semiconductor chip from being damaged and features thereof from being deteriorated due to projection of a laser beam thereon, when, for instance, the moisture drain hole is formed using a laser beam. Moreover, it is possible to prevent degradation of moisture resistance of the semiconductor chip due to the exposure to the outside-air.
Furthermore, the tentative protective wire is formed for covering a mouth of the moisture drain hole opened on the face for mounting the semiconductor chip so that the pit part formed by removing the tentative protective wire should have a width wider than the diameter of the moisture drain hole. Thus it is possible to drain moisture through the pit part and the moisture drain hole of the semiconductor device efficiently without enlarging the diameter of the moisture drain hole, compared to the case when the width of the pit part is as wide as the diameter of the moisture drain hole. This makes it possible to properly prevent, for instance, the intermediate layer or the mold resin from peeling off from the circuit board due to the expansion of the steam generated in the process of reflowing inside the semiconductor device.
A manufacturing method of a semiconductor device of the present invention including a circuit board provided with moisture drain hole formed therethrough and a semiconductor chip mounted on a face thereof via an intermediate layer (for instance an adhesive resin layer for fixing the semiconductor chip on the circuit board or a resin layer such as a solder resist layer), includes the steps of:
(a) forming a tentative protective wire and the moisture drain hole, the tentative protective wire being formed for covering a mouth of the moisture drain hole opened on the face, and the moisture drain hole being formed through the circuit board;
(b) after step (a), mounting the semiconductor chip on the face via an intermediate layer;
(c) after step (b), removing the tentative protective wire through the moisture drain hole.
According to this arrangement, the tentative protective wire is formed for covering a mouth of the moisture drain hole opened on the face, and the moisture drain hole is formed through the circuit board, in step (a). Either of forming the tentative protective wire and forming the moisture drain hole can be done before the formation of the other. Then in step (b) after step (a), the semiconductor chip is mounted on the face via an intermediate layer, and in step (c) after step (b), the tentative protective wire is removed by, for instance, etching through the moisture drain hole.
Consequently, it is possible in step (b) to prevent materials, for instance, the adhesive resin for fixing the semiconductor chip on the circuit board and resin materials such as the solder resist, contained in the intermediate layer from flowing out through the moisture drain hole, since the tentative protective wire covers a mouth of the moisture drain hole opened on the face.
Moreover, carrying out step (a) before step (b) prevents the semiconductor chip from being damaged and features thereof from being deteriorated due to projection of a laser beam thereon, when, for instance, the moisture drain hole is formed using a laser beam. Moreover, it is possible to prevent degradation of moisture resistance of the semiconductor chip due to the exposure to the outside-air.
Furthermore, the tentative protective wire is formed for covering a mouth of the moisture drain hole opened on the face for mounting the semiconductor chip so that the pit part formed by removing the tentative protective wire should have a width wider than the diameter of the moisture drain hole. Thus it is possible to drain moisture through the pit part and the moisture drain hole of the semiconductor device efficiently without enlarging the diameter of the moisture drain hole, compared to the case when the width of the pit part is as wide as the diameter of the moisture drain hole. This makes it possible to properly prevent, for instance, the intermediate layer or the mold resin from peeling off from the circuit board due to the expansion of the steam generated in the process of reflowing inside the semiconductor device.